During the drilling and completion of oil and gas wells, various wellbore treating fluids are used for a number of purposes. For example, high viscosity gels are used to create fractures in oil and gas bearing formations to increase production. High viscosity and high density gels are also used to maintain positive hydrostatic pressure in the well while limiting flow of well fluids into earth formations during installation of completion equipment. High viscosity fluids are used to flow sand into wells during gravel packing operations. The high viscosity fluids are normally produced by mixing dry powder and/or granular materials and agents with water at the well site as they are needed for the particular treatment. Systems for metering and mixing the various materials are normally portable, e.g., skid- or truck-mounted, since they are needed for only short periods of time at a well site.
The powder or granular treating material (bulk material) is normally transported to a well site in a commercial or common carrier tank truck. Once the tank truck and mixing system are at the well site, the bulk material must be transferred or conveyed from the tank truck into a supply tank for metering into a blender as needed. Well sites typically include one or more supply tanks that are filled pneumatically on location and then connected to the blender through a series of belts (or auger conveyors in some marine applications). The supply tanks provide a large connected capacity of bulk material to be supplied to the blender. Discharge gates on the supply tanks output bulk material from the supply tanks to the conveyors, which then meter the bulk material to the blender.
Recent developments in bulk material handling operations involve the use of portable containers for transporting dry material about a well location. The containers can be brought in on trucks, unloaded, stored on location, and manipulated about the well site when the material is needed. The containers are generally easier to manipulate on location than a large supply tank trailer. However, the many separate containers do not provide a large connected capacity to the blender and, therefore, the containers must be changed out frequently to complete a wellbore treatment process. It is important to coordinate movement of such bulk material containers about the well site and the release of desired bulk materials from the containers into the blender to successfully perform the wellbore treatment.